One benefit of many online communication channels over offline methods is that they enable communication among groups of people, rather than restricting communication to be peer-to-peer. Email is just one format that supports group conversations, but there are many others, such as photo- and link-sharing, and collaborative document editing. In fact, group communication is prevalent. An analysis of the Google Mail email network shows that over 10% of emails are sent to more than one recipient, and over 4% of emails are sent to 5 or more recipients. Within enterprise domains, group communication is even more critical. An analysis of the email network of Google employees showed that over 40% of emails are sent to more than one recipient, and nearly 10% are sent to 5 or more recipients.
As opposed to broadcast-style media, such as blogs and micro-blogging platforms like Twitter, the information communicated by an individual to a limited group is generally carefully targeted, and may be private. The recipient lists for small-group communications such as emails are selectively constructed by the message senders. Users tend to communicate repeatedly with the same groups of contacts.
Despite the prevalence of group communication, users do not often take the time to create and maintain custom contact groups. A survey of mobile phone users in Europe showed that only 16% of users have created custom contact groups on their mobile phones. See, M. Kuhn et al., “Cluestr: Mobile social networking for enhanced group communication,” In Proceedings of the International Conference on Supporting Group Work (GROUP), May 2009. In user studies, users explain that group-creation is time consuming and tedious. Additionally, groups change dynamically, with new individuals being added to multi-party communication threads and others being removed. Static, custom-created groups can quickly become stale, and lose their utility. Consequently, these static custom-created groups have limited utility in determining contacts to suggest for a draft message.